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Backflow Prevention

What is backflow prevention?

Backflow prevention is the term used to describe the prevention of an unwanted reverse flow of water from a potentially polluted source into the drinking water supply.  All properties within the drinking water supply network must have adequate backflow prevention.  Most residential properties have a backflow prevention valve within the property water meter.

When does backflow occur?  

Backflow occurs when a condition exists in a water supply system that will cause back-siphonage or back-pressure.  Back-siphonage can occur on a property through a vacuum created in the water supply system.  An example of back-siphonage would be a pipeline breakage, undersized pipework or high withdrawal rates.  Back-pressure can occur within properties when high pressure is generated downstream by pumps, thermal expansion or elevation.  There is potential for contamination via backflow from:  

  • Fire Hose Reels (FHR)
  • Irrigation systems  
  • Swimming pools
  • Vehicle maintenance pits
  • Ornamental ponds
  • Air conditioning towers
  • Vehicle/bin washing bays
  • Chemical injection areas
  • Alternative water supplies

Property owners have a responsibility to provide and maintain backflow prevention devices to protect the drinking water supply from the activities on your property.  Properties requiring backflow prevention include:

  • Vehicle repair workshops
  • Restaurants
  • Caravan parks
  • Public swimming pools
  • Medical, dental, and veterinary surgeries
  • Car and plant washing facilities  
  • Dry cleaners and laundries
  • Hospitals, mortuaries and funeral parlours
  • Schools
  • Abattoirs
  • Chemical plants and laboratories
  • Pathology laboratories
  • Food and beverage processing plants
  • Metal finishing plants
  • Petroleum processing or storage plants
  • Factories using, processing or manufacturing toxic chemicals
  • All premises with fire services

What is the safeguard to prevent a backflow occurrence?

A correctly selected backflow prevention device (one-way valve) will eliminate any risk of contamination of the drinking water supply.  Backflow devices are either testable or non-testable types with the selection dependent on the risk associated with the possible contamination.  Generally, backflow prevention should be installed if there is risk of contamination to the water supply. The type of backflow device must conform to AS/NZS3500.1:2018 Appendix F. You can identify if a backflow prevention device is installed on your property by checking the requirements stated on the plumbing approval given by the Councils' Plumbing Inspector.

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